This invention relates to metal working, and more particularly to the manufacture of cold-work hardened cylinders.
In certain environments, it is necessary to provide long cylinders of large diameter. For example, a super conductive excitation winding of a tubogenerator is cooled by liquid helium. The cold rotor body which supports the winding is located in an outer cylinder which is warm and non-magnetic. Turbogenerators of this type have a considerable length, and the cylinder in which the winding is located must therefore also be of great length. These long cylinders can be assembled from sections of shorter length, but the sections must be welded together to achieve the desired length. A disadvantage of the welding operation is that the desireable mechanical properties which are achieved by cold-working are lost due to the heat that is applied during the welding operation. This method of assembly is only suitable for cylinders of small diameter that are not subject to high stresses.
It is an object of this invention to provide a method for the manufacture of cold-worked cylinders which is economical and will not adversely affect the mechanical properties of the cylinder, and yet is suitable for cylinders of large diameters and great length.